From 6bf0a5cb5034a7e684dcc3500e841785237ce2dd Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 19:32:43 +0200 Subject: Adding upstream version 1:115.7.0. Signed-off-by: Daniel Baumann --- third_party/libwebrtc/rtc_base/buffer.h | 452 ++++++++++++++++++++++++++++++++ 1 file changed, 452 insertions(+) create mode 100644 third_party/libwebrtc/rtc_base/buffer.h (limited to 'third_party/libwebrtc/rtc_base/buffer.h') diff --git a/third_party/libwebrtc/rtc_base/buffer.h b/third_party/libwebrtc/rtc_base/buffer.h new file mode 100644 index 0000000000..6663c687b8 --- /dev/null +++ b/third_party/libwebrtc/rtc_base/buffer.h @@ -0,0 +1,452 @@ +/* + * Copyright 2004 The WebRTC Project Authors. All rights reserved. + * + * Use of this source code is governed by a BSD-style license + * that can be found in the LICENSE file in the root of the source + * tree. An additional intellectual property rights grant can be found + * in the file PATENTS. All contributing project authors may + * be found in the AUTHORS file in the root of the source tree. + */ + +#ifndef RTC_BASE_BUFFER_H_ +#define RTC_BASE_BUFFER_H_ + +#include + +#include +#include +#include +#include +#include + +#include "absl/strings/string_view.h" +#include "api/array_view.h" +#include "rtc_base/checks.h" +#include "rtc_base/type_traits.h" +#include "rtc_base/zero_memory.h" + +namespace rtc { + +namespace internal { + +// (Internal; please don't use outside this file.) Determines if elements of +// type U are compatible with a BufferT. For most types, we just ignore +// top-level const and forbid top-level volatile and require T and U to be +// otherwise equal, but all byte-sized integers (notably char, int8_t, and +// uint8_t) are compatible with each other. (Note: We aim to get rid of this +// behavior, and treat all types the same.) +template +struct BufferCompat { + static constexpr bool value = + !std::is_volatile::value && + ((std::is_integral::value && sizeof(T) == 1) + ? (std::is_integral::value && sizeof(U) == 1) + : (std::is_same::type>::value)); +}; + +} // namespace internal + +// Basic buffer class, can be grown and shrunk dynamically. +// Unlike std::string/vector, does not initialize data when increasing size. +// If "ZeroOnFree" is true, any memory is explicitly cleared before releasing. +// The type alias "ZeroOnFreeBuffer" below should be used instead of setting +// "ZeroOnFree" in the template manually to "true". +template +class BufferT { + // We want T's destructor and default constructor to be trivial, i.e. perform + // no action, so that we don't have to touch the memory we allocate and + // deallocate. And we want T to be trivially copyable, so that we can copy T + // instances with std::memcpy. This is precisely the definition of a trivial + // type. + static_assert(std::is_trivial::value, "T must be a trivial type."); + + // This class relies heavily on being able to mutate its data. + static_assert(!std::is_const::value, "T may not be const"); + + public: + using value_type = T; + using const_iterator = const T*; + + // An empty BufferT. + BufferT() : size_(0), capacity_(0), data_(nullptr) { + RTC_DCHECK(IsConsistent()); + } + + // Disable copy construction and copy assignment, since copying a buffer is + // expensive enough that we want to force the user to be explicit about it. + BufferT(const BufferT&) = delete; + BufferT& operator=(const BufferT&) = delete; + + BufferT(BufferT&& buf) + : size_(buf.size()), + capacity_(buf.capacity()), + data_(std::move(buf.data_)) { + RTC_DCHECK(IsConsistent()); + buf.OnMovedFrom(); + } + + // Construct a buffer with the specified number of uninitialized elements. + explicit BufferT(size_t size) : BufferT(size, size) {} + + BufferT(size_t size, size_t capacity) + : size_(size), + capacity_(std::max(size, capacity)), + data_(capacity_ > 0 ? new T[capacity_] : nullptr) { + RTC_DCHECK(IsConsistent()); + } + + // Construct a buffer and copy the specified number of elements into it. + template ::value>::type* = nullptr> + BufferT(const U* data, size_t size) : BufferT(data, size, size) {} + + template ::value>::type* = nullptr> + BufferT(U* data, size_t size, size_t capacity) : BufferT(size, capacity) { + static_assert(sizeof(T) == sizeof(U), ""); + if (size > 0) { + RTC_DCHECK(data); + std::memcpy(data_.get(), data, size * sizeof(U)); + } + } + + // Construct a buffer from the contents of an array. + template ::value>::type* = nullptr> + BufferT(U (&array)[N]) : BufferT(array, N) {} + + ~BufferT() { MaybeZeroCompleteBuffer(); } + + // Implicit conversion to absl::string_view if T is compatible with char. + template + operator typename std::enable_if::value, + absl::string_view>::type() const { + return absl::string_view(data(), size()); + } + + // Get a pointer to the data. Just .data() will give you a (const) T*, but if + // T is a byte-sized integer, you may also use .data() for any other + // byte-sized integer U. + template ::value>::type* = nullptr> + const U* data() const { + RTC_DCHECK(IsConsistent()); + return reinterpret_cast(data_.get()); + } + + template ::value>::type* = nullptr> + U* data() { + RTC_DCHECK(IsConsistent()); + return reinterpret_cast(data_.get()); + } + + bool empty() const { + RTC_DCHECK(IsConsistent()); + return size_ == 0; + } + + size_t size() const { + RTC_DCHECK(IsConsistent()); + return size_; + } + + size_t capacity() const { + RTC_DCHECK(IsConsistent()); + return capacity_; + } + + BufferT& operator=(BufferT&& buf) { + RTC_DCHECK(buf.IsConsistent()); + MaybeZeroCompleteBuffer(); + size_ = buf.size_; + capacity_ = buf.capacity_; + using std::swap; + swap(data_, buf.data_); + buf.data_.reset(); + buf.OnMovedFrom(); + return *this; + } + + bool operator==(const BufferT& buf) const { + RTC_DCHECK(IsConsistent()); + if (size_ != buf.size_) { + return false; + } + if (std::is_integral::value) { + // Optimization. + return std::memcmp(data_.get(), buf.data_.get(), size_ * sizeof(T)) == 0; + } + for (size_t i = 0; i < size_; ++i) { + if (data_[i] != buf.data_[i]) { + return false; + } + } + return true; + } + + bool operator!=(const BufferT& buf) const { return !(*this == buf); } + + T& operator[](size_t index) { + RTC_DCHECK_LT(index, size_); + return data()[index]; + } + + T operator[](size_t index) const { + RTC_DCHECK_LT(index, size_); + return data()[index]; + } + + T* begin() { return data(); } + T* end() { return data() + size(); } + const T* begin() const { return data(); } + const T* end() const { return data() + size(); } + const T* cbegin() const { return data(); } + const T* cend() const { return data() + size(); } + + // The SetData functions replace the contents of the buffer. They accept the + // same input types as the constructors. + template ::value>::type* = nullptr> + void SetData(const U* data, size_t size) { + RTC_DCHECK(IsConsistent()); + const size_t old_size = size_; + size_ = 0; + AppendData(data, size); + if (ZeroOnFree && size_ < old_size) { + ZeroTrailingData(old_size - size_); + } + } + + template ::value>::type* = nullptr> + void SetData(const U (&array)[N]) { + SetData(array, N); + } + + template ::value>::type* = nullptr> + void SetData(const W& w) { + SetData(w.data(), w.size()); + } + + // Replaces the data in the buffer with at most `max_elements` of data, using + // the function `setter`, which should have the following signature: + // + // size_t setter(ArrayView view) + // + // `setter` is given an appropriately typed ArrayView of length exactly + // `max_elements` that describes the area where it should write the data; it + // should return the number of elements actually written. (If it doesn't fill + // the whole ArrayView, it should leave the unused space at the end.) + template ::value>::type* = nullptr> + size_t SetData(size_t max_elements, F&& setter) { + RTC_DCHECK(IsConsistent()); + const size_t old_size = size_; + size_ = 0; + const size_t written = AppendData(max_elements, std::forward(setter)); + if (ZeroOnFree && size_ < old_size) { + ZeroTrailingData(old_size - size_); + } + return written; + } + + // The AppendData functions add data to the end of the buffer. They accept + // the same input types as the constructors. + template ::value>::type* = nullptr> + void AppendData(const U* data, size_t size) { + if (size == 0) { + return; + } + RTC_DCHECK(data); + RTC_DCHECK(IsConsistent()); + const size_t new_size = size_ + size; + EnsureCapacityWithHeadroom(new_size, true); + static_assert(sizeof(T) == sizeof(U), ""); + std::memcpy(data_.get() + size_, data, size * sizeof(U)); + size_ = new_size; + RTC_DCHECK(IsConsistent()); + } + + template ::value>::type* = nullptr> + void AppendData(const U (&array)[N]) { + AppendData(array, N); + } + + template ::value>::type* = nullptr> + void AppendData(const W& w) { + AppendData(w.data(), w.size()); + } + + template ::value>::type* = nullptr> + void AppendData(const U& item) { + AppendData(&item, 1); + } + + // Appends at most `max_elements` to the end of the buffer, using the function + // `setter`, which should have the following signature: + // + // size_t setter(ArrayView view) + // + // `setter` is given an appropriately typed ArrayView of length exactly + // `max_elements` that describes the area where it should write the data; it + // should return the number of elements actually written. (If it doesn't fill + // the whole ArrayView, it should leave the unused space at the end.) + template ::value>::type* = nullptr> + size_t AppendData(size_t max_elements, F&& setter) { + RTC_DCHECK(IsConsistent()); + const size_t old_size = size_; + SetSize(old_size + max_elements); + U* base_ptr = data() + old_size; + size_t written_elements = setter(rtc::ArrayView(base_ptr, max_elements)); + + RTC_CHECK_LE(written_elements, max_elements); + size_ = old_size + written_elements; + RTC_DCHECK(IsConsistent()); + return written_elements; + } + + // Sets the size of the buffer. If the new size is smaller than the old, the + // buffer contents will be kept but truncated; if the new size is greater, + // the existing contents will be kept and the new space will be + // uninitialized. + void SetSize(size_t size) { + const size_t old_size = size_; + EnsureCapacityWithHeadroom(size, true); + size_ = size; + if (ZeroOnFree && size_ < old_size) { + ZeroTrailingData(old_size - size_); + } + } + + // Ensure that the buffer size can be increased to at least capacity without + // further reallocation. (Of course, this operation might need to reallocate + // the buffer.) + void EnsureCapacity(size_t capacity) { + // Don't allocate extra headroom, since the user is asking for a specific + // capacity. + EnsureCapacityWithHeadroom(capacity, false); + } + + // Resets the buffer to zero size without altering capacity. Works even if the + // buffer has been moved from. + void Clear() { + MaybeZeroCompleteBuffer(); + size_ = 0; + RTC_DCHECK(IsConsistent()); + } + + // Swaps two buffers. Also works for buffers that have been moved from. + friend void swap(BufferT& a, BufferT& b) { + using std::swap; + swap(a.size_, b.size_); + swap(a.capacity_, b.capacity_); + swap(a.data_, b.data_); + } + + private: + void EnsureCapacityWithHeadroom(size_t capacity, bool extra_headroom) { + RTC_DCHECK(IsConsistent()); + if (capacity <= capacity_) + return; + + // If the caller asks for extra headroom, ensure that the new capacity is + // >= 1.5 times the old capacity. Any constant > 1 is sufficient to prevent + // quadratic behavior; as to why we pick 1.5 in particular, see + // https://github.com/facebook/folly/blob/master/folly/docs/FBVector.md and + // http://www.gahcep.com/cpp-internals-stl-vector-part-1/. + const size_t new_capacity = + extra_headroom ? std::max(capacity, capacity_ + capacity_ / 2) + : capacity; + + std::unique_ptr new_data(new T[new_capacity]); + if (data_ != nullptr) { + std::memcpy(new_data.get(), data_.get(), size_ * sizeof(T)); + } + MaybeZeroCompleteBuffer(); + data_ = std::move(new_data); + capacity_ = new_capacity; + RTC_DCHECK(IsConsistent()); + } + + // Zero the complete buffer if template argument "ZeroOnFree" is true. + void MaybeZeroCompleteBuffer() { + if (ZeroOnFree && capacity_ > 0) { + // It would be sufficient to only zero "size_" elements, as all other + // methods already ensure that the unused capacity contains no sensitive + // data---but better safe than sorry. + ExplicitZeroMemory(data_.get(), capacity_ * sizeof(T)); + } + } + + // Zero the first "count" elements of unused capacity. + void ZeroTrailingData(size_t count) { + RTC_DCHECK(IsConsistent()); + RTC_DCHECK_LE(count, capacity_ - size_); + ExplicitZeroMemory(data_.get() + size_, count * sizeof(T)); + } + + // Precondition for all methods except Clear, operator= and the destructor. + // Postcondition for all methods except move construction and move + // assignment, which leave the moved-from object in a possibly inconsistent + // state. + bool IsConsistent() const { + return (data_ || capacity_ == 0) && capacity_ >= size_; + } + + // Called when *this has been moved from. Conceptually it's a no-op, but we + // can mutate the state slightly to help subsequent sanity checks catch bugs. + void OnMovedFrom() { + RTC_DCHECK(!data_); // Our heap block should have been stolen. +#if RTC_DCHECK_IS_ON + // Ensure that *this is always inconsistent, to provoke bugs. + size_ = 1; + capacity_ = 0; +#else + // Make *this consistent and empty. Shouldn't be necessary, but better safe + // than sorry. + size_ = 0; + capacity_ = 0; +#endif + } + + size_t size_; + size_t capacity_; + std::unique_ptr data_; +}; + +// By far the most common sort of buffer. +using Buffer = BufferT; + +// A buffer that zeros memory before releasing it. +template +using ZeroOnFreeBuffer = BufferT; + +} // namespace rtc + +#endif // RTC_BASE_BUFFER_H_ -- cgit v1.2.3